Chapter 2: Chemistry Comes Alive – Foundations for Anatomy & Physiology

Introduction to Basic Chemistry in Anatomy & Physiology

This chapter introduces the essential chemical principles that underpin the structure and function of the human body. Understanding these concepts is crucial for comprehending physiological processes at the molecular and cellular levels.

Objectives

• Define key terminology used in basic chemistry.

• Identify the four major elements that make up the human body.

• Compare common elements and trace elements in the body.

• Use the Periodic Table to determine atomic structure and stability.

• Distinguish between compounds and mixtures.

• Describe types of chemical bonds and reactions.

• Explain the structure and properties of water, acids, bases, and buffers.

• Describe the relationship between monomers and polymers in macromolecules.

• Explain the role of enzymes and ATP in cellular processes.

Matter and Its States

Definition and Properties of Matter

• Matter is anything that has mass and occupies space.

• Matter can be seen, smelled, and/or felt.

• Weight is mass plus the effects of gravity.

States of Matter

• Solid: Definite shape and volume.

• Liquid: Changeable shape; definite volume.

• Gas: Changeable shape and volume.

Energy

Definition and Forms

• Energy is the capacity to do work or put matter into motion.

• The greater the work done, the more energy is used up.

Energy Form Conversion

• Energy may be converted from one form to another.

• Energy conversion is often inefficient, with some energy lost as heat.

Atoms and Elements

Structure of Atoms

• Elements are unique building blocks for each type of matter.

• Atoms are the smallest particles of an element that retain its properties.

• Atoms are composed of three subatomic particles:

  • Protons (positive charge)

  • Neutrons (neutral)

  • Electrons (negative charge)

Common Elements in the Human Body

The human body is primarily composed of four elements: oxygen, carbon, hydrogen, and nitrogen. Several other elements are present in smaller amounts and are essential for various physiological functions.

Element	Atomic Symbol	Approx. % Body Mass	Functions
Oxygen	O	65.0	Component of both organic (carbon-containing) and inorganic molecules; needed for ATP production.
Carbon	C	18.5	Component of all organic molecules (carbohydrates, lipids, proteins, nucleic acids).
Hydrogen	H	9.5	Component of all organic molecules; influences pH of body fluids.
Nitrogen	N	3.3	Component of proteins and nucleic acids.

Additional info: Other important elements include calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chlorine (Cl), magnesium (Mg), and trace elements such as iron (Fe), iodine (I), and zinc (Zn).

Functions of Selected Elements

Element	Function
Calcium (Ca)	Found in bones/teeth; required for muscle contraction, nerve conduction, blood clotting.
Phosphorus (P)	Part of bones/teeth, nucleic acids, ATP, and phospholipids.
Potassium (K)	Major positive ion in cells; necessary for nerve impulses and muscle contraction.
Sodium (Na)	Major positive ion in extracellular fluids; important for water balance and nerve/muscle function.
Chlorine (Cl)	Most abundant negative ion in extracellular fluids.
Magnesium (Mg)	Cofactor in many metabolic reactions.

Atomic Number and Mass Number

• Atomic number: Number of protons in the nucleus; written as a subscript to the left of the atomic symbol.

• Mass number: Total number of protons and neutrons; written as a superscript to the left of the atomic symbol.

• Isotopes: Atoms with the same number of protons but different numbers of neutrons.

Compounds and Mixtures

Definitions

• Molecule: Two or more atoms bonded together.

• Compound: Molecule with two or more different kinds of atoms bonded together.

• Mixture: Two or more components physically intermixed.

Types of Mixtures

• Solutions: Homogeneous mixtures (e.g., saline solution).

• Colloids: Heterogeneous mixtures with larger particles (e.g., cytosol).

• Suspensions: Heterogeneous mixtures with visible solutes that settle out (e.g., blood).

Differences Between Mixtures and Compounds

• Mixtures do not involve chemical bonding; compounds do.

• Mixtures can be separated by physical means; compounds require chemical changes.

• Mixtures can be heterogeneous or homogeneous; compounds are always homogeneous.

Chemical Bonds

Types of Chemical Bonds

• Ionic bonds: Transfer of electrons from one atom to another, resulting in charged ions.

• Covalent bonds: Sharing of electrons between atoms. Can be single, double, or triple bonds.

• Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Polar vs. Nonpolar Covalent Bonds

• Nonpolar: Electrons shared equally (e.g., O2).

• Polar: Electrons shared unequally, creating partial charges (e.g., H2O).

Chemical Reactions

Types of Chemical Reactions

• Synthesis (Anabolic): Atoms or molecules combine to form larger, more complex molecules.

• Decomposition (Catabolic): Molecules are broken down into smaller molecules or atoms.

• Exchange (Displacement): Bonds are both made and broken; atoms are exchanged between molecules.

• Redox (Oxidation-Reduction): Involves transfer of electrons between atoms/molecules.

Energy Flow in Reactions

• Exergonic: Release energy (catabolic, oxidative reactions).

• Endergonic: Absorb energy (anabolic reactions).

Reversibility and Reaction Rates

• Most reactions are theoretically reversible, but many biological reactions are not due to high energy requirements or removal of products.

• Reaction rates are affected by temperature, concentration, particle size, and catalysts (enzymes).

Inorganic and Organic Compounds

Inorganic Compounds

• Do not contain carbon (exceptions: CO2, CO).

• Include water, salts, acids, and bases.

Properties of Water

• High heat capacity and heat of vaporization.

• Excellent solvent; forms hydration layers.

• Involved in hydrolysis and dehydration synthesis reactions.

• Provides cushioning (e.g., cerebrospinal fluid).

Salts, Acids, and Bases

• Salts: Ionic compounds that dissociate in water to form electrolytes.

• Acids: Proton donors; release H+ in solution.

• Bases: Proton acceptors; release OH- in solution.

pH Scale

• Measures hydrogen ion concentration; scale is logarithmic (each unit = 10-fold change).

• pH < 7: acidic; pH = 7: neutral; pH > 7: basic (alkaline).

Buffers

• Resist changes in pH by releasing or binding H+.

• Example: Carbonic acid-bicarbonate buffer system in blood.

Organic Compounds

• Contain carbon; usually large and covalently bonded.

• Include carbohydrates, lipids, proteins, and nucleic acids.

Monomers and Polymers

• Monomers are building blocks; polymers are chains of monomers.

• Formed by dehydration synthesis; broken down by hydrolysis.

Macromolecules

Carbohydrates

• Include sugars and starches; contain C, H, O (2:1 H:O ratio).

• Monosaccharides: Single sugars (e.g., glucose).

• Disaccharides: Two sugars (e.g., sucrose).

• Polysaccharides: Many sugars (e.g., starch in plants, glycogen in animals).

Lipids

• Contain C, H, O (less O than carbohydrates); sometimes P.

• Insoluble in water.

• Types: triglycerides (fats/oils), phospholipids, steroids, eicosanoids.

• Triglycerides: Glycerol + 3 fatty acids; energy storage, insulation, protection.

• Phospholipids: Glycerol + 2 fatty acids + phosphate group; major component of cell membranes.

• Steroids: Four interlocking rings; cholesterol is the most important steroid.

• Eicosanoids: Derived from arachidonic acid; include prostaglandins (inflammation, blood clotting).

Proteins

• Comprise 10-30% of cell mass; contain C, H, O, N, sometimes S and P.

• Polymers of amino acids joined by peptide bonds.

• Levels of structure: primary, secondary, tertiary, quaternary.

• Fibrous proteins: Structural, water-insoluble (e.g., collagen).

• Globular proteins: Functional, water-soluble (e.g., enzymes, antibodies).

• Denaturation: Loss of 3D structure and function due to pH or temperature changes.

Enzymes

• Globular proteins that act as biological catalysts.

• Speed up reactions by lowering activation energy.

• Highly specific for substrates; names often end in -ase.

• Consist of an apoenzyme (protein) and a cofactor/coenzyme (non-protein component).

Nucleic Acids

• Composed of C, H, O, N, P; largest molecules in the body.

• Polymers of nucleotides.

• DNA: Double-stranded helix; genetic blueprint; located in nucleus.

• RNA: Single-stranded; involved in protein synthesis; types include mRNA, tRNA, rRNA.

Characteristic	DNA	RNA
Location	Nucleus	Cytoplasm
Function	Genetic material; directs protein synthesis	Carries out genetic instructions for protein synthesis
Structure	Double-stranded helix	Single-stranded
Sugar	Deoxyribose	Ribose
Bases	A, G, C, T	A, G, C, U

ATP (Adenosine Triphosphate)

• Energy currency of the cell.

• Composed of adenine, ribose, and three phosphate groups.

• Energy is released when phosphate bonds are broken: $\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

• Powers cellular work such as muscle contraction, transport, and synthesis reactions.